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The purple martin, a swallow, is arriving now in Tennessee, with reports of "scouts" logged almost daily online.

Purple martins, the largest of the swallows in North America faithfully return to the same locations each year from wintering grounds in South America. Tennesseans have a long tradition of hosting purple martinsand boasts what may be the largest colony in North America -- over 700 pairs -- near Finger in McNairy County, and is the site of an annual festival in June.

Because martins are totally dependent on humans for housing, "landlords" anxiously await their return each year and post reports of dates/locations of "scouts" on an online data base (purplemartin.org) maintained by the Purple Martin Conservation Association (PMCA), a nonprofit conservation.

The earliest arriving purple martin this year was reported from Finger on Feb. 17, a very early bird. Subsequent early reports: Feb. 20 in Memphis, Feb. 21 Maryville, and Feb. 26 Covington.

Early birds

Hobbyists marvel at the returns each year and sometimes wonder how a martin can get here so quickly after the first few warm days of spring. New research in which the PMCA participated gives some clues.

Published recently in the journal Science, a female martin -- fitted with a tiny "geo-locater" -- returned in spring from central Brazil to Pennsylvania in just 13 days, astounding professional researchers. Apparently with a warm tail wind, a martin can cover well over 300 miles a day in returning north in spring.

The first wave of arrivals each year consists of so-called "adult" martins -- those 2 or more years old, with adult males sporting full dark-purple color. Females are a bit drab, with a gray breast.

One-year-old martins, called "sub adults," arrive 10 to 12 weeks later than the older birds, in April and May. These younger birds are more easily attracted to new housing locations.

Population increasing

The term "scout" actually is a misnomer. These are simply older experienced birds that are eager to reclaim their housing. Some arrive dangerously early and may perish when cold temperatures clear the air of flying insects. Fortunately for the martins, many landlords today offer supplemental feeding of thawed crickets, live mealworms or even small bits of scrambled eggs flung into the air from a plastic spoon -- and after martins learn the drill -- from elevated platforms or placed in compartments.

Purple martins prefer to nest in colonies in gourds hung from large racks and in multi-compartment birdhouses in open yards. As a species, purple martins are relatively common throughout Tennessee, with the greatest numbers found in the western part of the state, according to North American Breeding Bird survey.

The PMCA recently analyzed long-term data from the North American Breeding Bird Survey (BBS) and found that -- thanks to devoted men and women who erect and maintain housing -- purple martin populations overall are holding steady in North America, with exceptions in some states, and appear to be increasingly steadily in Tennessee.

However, despite relative abundance in the state, many people try for years to attract purple martins without success, or their colonies disappear. Hobbyists may be unaware that problems such as competition from invasive non-native birds, including European starlings and House Sparrows, or predation from raccoons or rat snakes caused abandonment.

While generations of Americans have hosted purple martins -- the custom adopted from Native Americans who hung out nesting gourds -- specific techniques to help a colony thrive emerged in the past decade, based on research conducted by the PMCA and landlords in the field.

Among innovations are deeper compartments to protect nestlings from rain and aerial predators such as owls, specially-shaped entrance holes designed to admit martins while excluding starlings -- and unique pole guards to thwart rat snakes and raccoons which are common in Tennessee.

On the fly

Because purple martins are birds of the open sky, catching insects on the fly, the PMCA's number one tip: place housing in the most open space available, but where the colony can be enjoyed and monitored.

More information about purple martins can be obtained from the Purple Martin Conservation Association -- which is focused on aiding martins and landlords -- including a products catalog and information booklet, with advice on attracting and managing a colony, and data sheets to participate in "Project MartinWatch" a national effort in which participants monitor nests and mail information to the PMCA at season's end. To obtain the booklet, contact the PMCA at 814-833-7656 or online at purplemartin.org.